Shutter for image projection system

ABSTRACT

An image projection system comprises an image projector, such as a film or television projector and a projection screen. The projection screen is fabricated of a substantially transparent material, such as glass or plastic. The screen of transparent material has one or more areas or portions formed therein which areas or portions may be made to be translucent upon the application of a stimulus. Once in a translucent condition, the projected image can be received and viewed on the translucent portion. A mirror can be positioned behind the projection screen so that a person can view the reflection of themselves in the mirror when the screen is transparent, and an image can be projected when the projection screen is made to be substantially translucent.

CROSS REFERENCE TO RELATED APPLICATION

The present application is a continuation-in-part of U.S. patentapplication Ser. No. 09/876,400 now allowed, entitled “Image ProjectionSystem” filed Jun. 7, 2001.

TECHNICAL FIELD

The present invention is generally related to the field of imageprojection systems.

BACKGROUND INFORMATION

In U.S. patent applications Ser. Nos. 09/519,537 and 09/876,400, aninvention was disclosed whereby a substantially transparent medium couldbe used as a projection screen for capturing an image from an imageprojector. When the medium was not capturing an image from an imageprojector, its substantially transparent characteristic permittedpersons to see through the medium. However, the system also provided anability for the medium to capture an image from an image projector forviewing by persons. In one embodiment, the medium was made to have acharacteristic that caused it to be nearly opaque, or substantiallytranslucent (permitting the passage of light, but not sufficient as tobe able to view objects clearly), so that persons could see clearly theimage projected.

The present invention takes the advantages of this system to furtheruses.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawings, in which:

FIG. 1 illustrates a prospective view of a projection screen inaccordance with the present invention;

FIG. 2 illustrates a side view of the projection screen shown in FIG. 1;

FIG. 3 is a side view of an image projection system;

FIG. 4 illustrates an alternative embodiment of the present invention;

FIG. 5 illustrates an embodiment of the present invention;

FIG. 6 illustrates a flow diagram of an embodiment of the presentinvention;

FIGS. 7A-7E illustrate alternative embodiments of the present invention;and

FIG. 8 illustrates a circuit diagram of a video controlled shutter.

DETAILED DESCRIPTION

In the following description, numerous specific details are set forthsuch as specific materials to provide a thorough understanding of thepresent invention. However, it will be obvious to those skilled in theart that the present invention may be practiced without such specificdetails. In other instances, well-known circuits have been shown inblock diagram form in order not to obscure the present invention inunnecessary detail. For the most part, details concerning timingconsiderations and the like have been omitted in as much as such detailsare not necessary to obtain a complete understanding of the presentinvention and are within the skills of persons of ordinary skill in therelevant art.

While the specification concludes with claims defining the features ofthe invention that are regarded as novel, it is believed that theinvention will be better understood from a consideration of thefollowing description in conjunction with the drawing figures, in whichlike reference numerals are carried forward.

Referring now to FIG. 3, there is illustrated therein a cross-sectionalside view of the image projection system 300 as disclosed in U.S. patentapplication Ser. No. 09/876,400. The system 300 comprises a projector301 of any type commonly used, examples of which include an LCDprojector, a television projector currently used on conventionalprojection television systems, a film projector, a slide projector or acomputer for providing computer generated images, to name but a few. Thesystem 300 further includes a projection screen 101. However, theprojection screen herein is a glass or other transparent (orsemi-transparent) material, having one or more switchable portions. Moreparticularly, the screen 101 may comprise a sheet of glass having aportion 102 or portions that can be switched between the glass' typicaltransparent characteristic, to a translucent appearance or condition.Projector 301 may project an image onto portion 102, which will beviewable by viewers on both sides of screen 101 when portion 102 istranslucent, on the right side when it is opaque. Alternatively, whenportion 102 is translucent or opaque, another projector 302 can be usedto project an image onto the other side of screen 101 so that such animage is viewable by viewers on the left side of screen 101.

The invention is also applicable for projection on reflective surfacessuch as mirrors.

As is readily apparent, light, as from a projected image, projected ontoa sheet of glass or other transparent material leaves no readilyviewable impression. This is due of course to the fact that theprojected light passes substantially unimpeded through the glass.Accordingly, heretofore retail establishments, for example, having largeareas of display glass windows were forced to post paper signadvertising, for example, an on-going sale. This type of advertising isneither dynamic, nor particularly effective. Conversely, an advertisingscheme taking advantage of the projection system described herein hasmany advantages. In particular, by projecting an image onto thetranslucent area of the glass substrate, the projected image is visibleby viewers on both sides of the glass. Moreover, while only a portion ofthe glass or other substrate may by switchable between the transparentand the translucent condition, the whole of the substrate may in fact beswitchable. This allows a condition in which, for example, a glass panebecomes an entire wall of e.g., advertising area.

Referring now to FIGS. 1 and 2, the transparent screen 101 may be aglass panel such as a display window, or some other type of transparentmedium. Examples of such transparent media include various types ofplastics, cast or fabricated as plastic sheets. The switchable portion102 switches between the transparent (or semi-transparent) state, whichis unsuitable for the receipt of a projected image, to a translucent oropaque state which will readily receive a projected image.

The switchable portion 102 may be provided by equipping the transparentscreen 101 with an electrical, chemical or photosensitive material whichis transparent in the absence of a stimulus, but switches to atranslucent or opaque state upon receipt of a particular stimulus.Examples of electrochromic, photochromic, and electrophoretic materialswhich may be advantageously employed in this function are well known tothose of ordinary skill in the art. For example, a polymer dispersedliquid crystal material as is commonly available may be sandwichedbetween sheets of glass or plastic in one or more portions of atransparent sheet. As oriented in the standard configuration, themolecules of liquid crystal material will allow for the passage of lightthere through, i.e., the portion is transparent. However, uponapplication of a relatively small electrical stimulus, the molecules ofliquid crystal material may be made to change their orientation, thustaking on a translucent or nearly opaque appearance and making such areaof the transparent sheet suitable for the receipt of a projected image.Such switchable materials are disclosed within J. W. Doane et al.,Displays from a New Type of Liquid Crystal Microdroplet Dispersion,IEEE, 1985 International Display Research Conference, pp. 153-154(1985); J. W. Doane et al., Wide-Angle-View PDLC Displays, SID 90DIGEST, pp. 224-226 (1990); Z. Yaniv et al., Active Matrix PolvinerDispersed Liquid Crystal Display, JAPAN DISPLAY, pp. 572-575 (1989),which are all incorporated by reference herein.

Alternatively, the medium 101 may be coated with a special resin calleda photopolymer which is capable of refracting light in the manner of aprism. The screen is configured to polarize the incident light fallingon different areas of the screen (angle of incidence at screen centermay be 35°) so that it emerges from the front evenly to produce a brightand clear image with a high degree of uniformity. Thus, when theprojector is off, light entering the medium in a substantiallyperpendicular manner will be allowed to pass through so that a personcan see directly through the medium. However, if an image is projectedat a specified angle to the medium, such an image is projected onto themedium for viewing. Such a projection system is available commerciallyfrom Hitachi.

While FIGS. 1, 2 and 3 illustrate but a single switchable portion 102 onthe transparent sheet 101, it is to be understood that the invention isnot so limited. For example, and as is illustrated in FIG. 4, aplurality of image projectors 404, 405 may be used to provide aplurality of projected images onto a plurality of switchable portions402, 403 of a transparent sheet 401 or plural sheets. Such an embodimentwould have great utility in, for example, retail settings.

In yet another embodiment, two or more portions may be arranged in anoverlapping relationship. This overlapping relationship may be either asituation in which two portions directly overlay one another, orpartially do so. If two overlay one another completely, such aconfiguration may be employed to allow images to be projected indiffering light conditions. For example, the first portion may be adarker translucent portion for better image quality in a first set oflight conditions, while the second portion may be a lighter translucentportion adapted for a second set of light conditions. Each of theportions would of course be independently controllable.

Referring to FIG. 5, there is illustrated a projection system inaccordance with the present invention whereby an image projector 501 isprojecting an image onto portion 102 of medium 101. A microcontroller orpersonal computer (PC) 503 may control what images are projected byprojector 501, and may control a shutter 502 so that projector 501 canremain continuously on, without having to be turned on and off, andmerely provide for the projection of the image out of the projector 501in accordance with the algorithm as described below with respect to FIG.6. Simultaneously, when the shutter 502 is opened, the medium 101 can bemade to have its portion 102 be translucent for receipt of the projectedimage. Furthermore, if a shutter is not used, there may be a residualleaking of light projected from the projector onto the screen, thuscausing a noticeable light spot. Use of the shutter maintains a “true”black image on the screen when there is no video.

The shutter 502 can be controlled to open only when the video source isactually projecting an image. Such a video source could be a videotape,DVD, or any other source that provides a video signal. In addition, theswitching of the medium from translucent to transparent and vice versacan also be made dependent upon the presence of a video signal sendingvideo images.

Referring to FIG. 8, there is illustrated an embodiment of a circuitthat can accomplish the foregoing. Such a circuit could be implementedanywhere within the systems described herein. Video is received at JackJ1 and looped through via jack J2. Capacitor C1 AC couples the videosignal to the amplifier A1 while resistor R2 provides a DC reference.Resistors R3 and R4 are used to provide a fixed DC offset to theamplifier A1 that in turns saturates the AC signal to the power supplyrails. Transistor Q1 converts the digitized AC signal while thecombination of resistors R6 and R7 and capacitor C3 provide furtherdelay to insure a more digitized AC signal. The basic function of thisportion of this circuit is to provide an asserted digital signal (e.g.,a high or 1 signal) when any form of an AC signal has been received atjack J1, and a negated digital signal (e.g., a low or 0 signal) whenthere is no AC signal (e.g., no video signal).

The combination of inverter 11, diode D1, resistor R8 and capacitor C4provides a first past delay while inverter 11, diode D2, resistor R10,resistor R11, and capacitor C6 provide an adjustable delay for whenthere is a brief blank space (i.e., no video signal) imbedded within thevideo stream received at jack J1. This reduces false triggering of theshutter and window control signals as discussed below. Inverter 13provides further buffering to inverters 14 and 15. Switch S2 is used toplace the window control and shutter control signals in either a manualmode (i.e., window off and shutter open) or an automatic mode. Anautomatic mode turns the window control signal on or off and closes oropens the shutter control signal depending on whether or not a videosignal has been detected. For example, when a video signal is detectedat jack J1, the shutter control signal will transition to an openshutter state, and the window control signal will switch to atranslucent state. Transistor Q2 is used as a high current driver forthe control signals, while diode D4 is a status LED indicating when theshutter control signal is active.

The circuitry encompassing switch S1, AC male plug J3, fuse F1, thetransformer, bridge, capacitors C7 and C8, resistor R17 and diode D5function as a basic AC to DC converter used to supply overall power tothe remainder of the circuitry in FIG. 8.

The circuit in FIG. 8 applies to a single video signal. For videosources with multiple video signals, such as RGB or S-video, the portionof this circuit comprising jacks J1 and J2, resistors R6 and R7 andcapacitor C1 can be duplicated for the required number of multiple videosources and electrically OR'd to the remainder of the circuit.

FIG. 6 illustrates a flow diagram of this process. In step 601,microcontroller 503 will send an image to projector 501. In step 602,the image is projected by projector 501. In step 603, substantiallysimultaneously with the opening of the shutter in step 604 the portion102 is transformed (optionally, in response to the window control signalfrom circuit 800) to a translucent state for receipt of the projectedimage. In step 604, shutter 502 is opened by circuit 800 using theshutter control signal. The sequence of steps 602, 603 and 604 can beinterchangeable. For example, the process could first switch the screento a translucent state, then open the shutter, and then project theimage. At a later time, in step 606 the shutter 502 will be closed inresponse to circuit 800 stopping projection 606 of the image (step 605).Substantially simultaneously with step 606 portion 102 of screen 101will be switched to a transparent state (optionally, in response tocircuit 800). In a manner similarly as described above, steps 605, 606and 607 are interchangeable.

Referring to FIG. 7A, there is illustrated an alternative embodiment ofthe present invention where screen 101 is placed in front of a mirror701 shown in sideview. As a result, when screen 101 is in a transparentstate, viewer 702 will see a reflection of the viewer. When screen 101is placed in a translucent state and shutter 502 is opened to allowprojection of an image from projector 501, viewer 702 will see theprojected image onto screen 101.

As an example, referring to FIG. 7B there is shown a front view of thesystem in FIG. 7A where a viewer 702 sees himself/herself through thetransparent screen 101 within the mirror 701. FIG. 7C illustrates thesystem when an image is projected onto screen 101 so that viewer 702 nowsees the projected image.

FIGS. 7D and 7E illustrate an alternative embodiment of the presentinvention where screen 101 is positioned in front of mirror 701 so thatwhen the screen 101 is in a transparent state, with no image beingprojected, the viewer 702 sees himself/herself in mirror 701. FIG. 7Eillustrates the projection of a clothing article, such as a dress 705,projected onto screen 101 so that viewer 702, who sees himself/herselfpartially in mirror 701, can view himself/herself in a virtual imagewith the dress.

Alternatively, a film implementing the properties of screen 101 could beattached directly onto the glass surface of the mirror.

Furthermore, screen 101 could be positioned so that it is incognito andthus does not present an image to be reflected in mirror 701. Then, whenan image is projected onto screen 101 (maybe in reverse), it will bereflected by mirror 701, and viewed by persons.

Note, all of the projectors described herein could operate with ashutter implemented as described with respect to FIG. 8. Also, anyprojector with a shutter can operate in this manner, without the needfor screen 101.

Although the present invention and its advantages have been described indetail, it should be understood that various changes, substitutions andalterations can be made herein without departing from the spirit andscope of the invention as defined by the appended claims.

What is claimed is:
 1. An image projection system comprising: a screen;a projector for projecting an image; and a shutter for permittingpassage of the image from the projector to the screen, the shutterautomatically opening upon receipt of a video image by the projector,and automatically closing when the video image is not received by theprojector.
 2. The system as recited in claim 1, wherein the screenfurther comprises a material that reflects the image when it isprojected at an angle relative to the screen.
 3. The system as recitedin claim 1, wherein the screen further comprises a material that issubstantially transparent when the screen is configured to allow theobject to be viewed through the screen, and wherein the material issubstantially translucent when the image is projected upon it.